BASIC FIBROBLAST GROWTH-FACTOR INHIBITS BASAL AND TRANSFORMING GROWTH-FACTOR-BETA INDUCED COLLAGEN ALPHA-2(I) GENE-EXPRESSION IN SCLERODERMA AND NORMAL FIBROBLASTS

Objective. Studies have shown that scleroderma (systemic sclerosis, SS c) and normal fibroblasts respond differently to basic fibroblast grow th factor (bFGF), SSc fibroblasts being less responsive than normal fi broblasts in mitogenic assays in vitro. bFGF also stimulates the expre ssion of platelet derived growth factor-alpha (PDGF-alpha) receptors i n normal fibroblasts, but not in SSc fibroblasts. Conversely, transfor ming growth factor-beta (TGF-beta) stimulates PDGF-alpha receptor expr ession in SSc fibroblasts, but not in normal fibroblasts. Since bFGF h as been shown to inhibit collagen gene expression in several cell type s, we examined responses of SSc and normal fibroblasts to bFGF alone a nd in combination with TGF-beta with regard to collagen alpha 2(I) (CO L1A2) expression. Methods. Fibroblasts were obtained by skin biopsy fr om affected areas of patients with diffuse cutaneous SSc and from heal thy donors and propagated in vitro. The effects of bFGF and TGF-beta o n the COL1A2 mRNA expression levels in SSc and healthy fibroblasts wer e analyzed by Northern blot. The effects of bFGF on the COL1A2 promote r activities in both cell types were analyzed by transient transfectio n assays. The effects of bFGF and TGF-beta on collagen protein synthes is were analyzed by sodium dodecyl sulfate polyacrylamide gel electrop horesis and fluorography. Results, While bFGF diminished COL1A2 mRNA i n both SSc and normal cells, COL1A2 mRNA quantities in the SSc fibrobl asts were not depressed to the levels expressed by normal controls. As anticipated, TGF-beta strongly induced COL1A2 mRNA levels in normal f ibroblasts, and to a lesser degree in SSc fibroblasts. When cells were incubated with both TGF-beta and bFGF, the stimulatory effect of TGF- beta was completely suppressed in both cell types. bFGF decreased COL1 A2 promoter activity in both cell types, suggesting that COL1A2 inhibi tion by bFGF occurs at least partially at the transcriptional level. T he effects of bFGF and TGF-beta on the collagen protein synthesis corr elated well with mRNA data, in that TGF-beta stimulated, while bFGF st rongly inhibited, collagen synthesis. Conclusion. bFGF is a potent inh ibitor of basal and TGF-beta stimulated collagen expression in human f ibroblasts, and this effect is not different between SSc and healthy f ibroblasts.